• H. Hassanzadegan, N. Garmendia
  ESS Bilbao, Bilbao
• F.J. Bermejo
  Bilbao, Faculty of Science and Technology, Bilbao
• M. Eguiraun
  ESS-Bilbao, Zamudio
• V. Etxebarria
  University of the Basque Country, Faculty of Science and Technology, Bilbao
• D.J.S. Findlay, A.P. Letchford
  STFC/RAL/ISIS, Chilton, Didcot, Oxon

Design, implementation and some practical results of the pulsed digital LLRF system (amplitude, phase and tuning loops) of the RFQ for the ISIS front end test stand are presented. The design is based on a fast analog front-end for RF-baseband conversion and a model-based Virtex-4 FPGA unit for signal processing and PI regulation. Complexity of the LLRF timing is significantly reduced and the LLRF requirements are fulfilled by utilizing the RF-baseband conversion method compared to the conventional RF-IF approach. Validity of the control loops is ensured practically by hardware-in-the-loop co-simulation of the system in MATLAB-Simulink using an aluminium mock-up cavity. It was shown through extensive tests that the LLRF system meets all the requirements including amplitude and phase stability, dynamic range, noise level and additionally provides a full amplitude and phase control range and a phase margin larger than 90 degrees for loop stability.

• A.P. Letchford, M.A. Clarke-Gayther, D.C. Faircloth, S.R. Lawrie, M. Perkins, P. Wise
  STFC/RAL/ISIS, Chilton, Didcot, Oxon
• S.M.H. Alsari, S. Jolly, D.A. Lee, P. Savage
  Imperial College of Science and Technology, Department of Physics, London
• I. Ariz, R. Enparantza, P. Romano, A. Sedano
  Fundación TEKNIKER, Eibar (Gipuzkoa)
• J.J. Back
  University of Warwick, Coventry
• F.J. Bermejo
  Bilbao, Faculty of Science and Technology, Bilbao
• M. Eguiraun
  ESS-Bilbao, Zamudio
• V. Etxebarria
  University of the Basque Country, Faculty of Science and Technology, Bilbao
• C. Gabor, D.C. Plostinar
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• N. Garmendia, H. Hassanzadegan
  ESS Bilbao, Bilbao
• A. Kurup
  Fermilab, Batavia
• J.K. Pozimski
  STFC/RAL, Chilton, Didcot, Oxon

The Front End Test Stand (FETS) under construction at the Rutherford Appleton Laboratory is the UK's contribution to research into the next generation of High Power Proton Accelerators (HPPAs). HPPAs are an essential part of any future Spallation Neutron Source, Neutrino Factory, Muon Collider, Accelerator Driven Sub-critical System, Waste Transmuter etc. FETS will demonstrate a high quality, high intensity, chopped H-minus beam and is a collaboration between RAL, Imperial College and the Universtity of Warwick in the UK and the Universidad del Pais Vasco in Spain. This paper describes the current status and future plans of FETS.

• I. Bustinduy, N. Garmendia, H. Hassanzadegan, D. de Cos
  ESS Bilbao, Bilbao
• F.J. Bermejo
  Bilbao, Faculty of Science and Technology, Bilbao
• V. Etxebarria, J. Portilla
  University of the Basque Country, Faculty of Science and Technology, Bilbao
• J. Feuchtwanger
  ESS-Bilbao, Zamudio
• S. Jolly, J.K. Pozimski, P. Savage
  Imperial College of Science and Technology, Department of Physics, London
• A.P. Letchford
  STFC/RAL/ISIS, Chilton, Didcot, Oxon

The main objective of the Bilbao Front End Test Stand (ETORFETS) is to set up a facility to demonstrate experimentally the design ideas for the future ESS LINAC that are being proposed in discussion forums by the technical scientific community. ETORFETS is focused on the first stage of the linear accelerator, namely, that of the Radio-Frequency Quadrupole (RFQ) and its pre and post beam transport systems. The RFQ bunches, focuses transverse and longitudinally, and accelerates charged particles in the low-energy range (up to ~ 3 MeV), thus becoming one of the main components of the accelerating structure. The first RFQ simulations, performed in Superfish and GPT software packages, will be presented in this work.